The invention relates to an at least substantially metallic cylinder head gasket with a gasket plate having at least one sheet metal layer and at least one through-opening which, for sealing around the through-opening, is enclosed by a ring-shaped sealing element which is pressed when the cylinder head gasket is installed between engine component sealing surfaces.
The gasket plates of such cylinder head gaskets usually have several such through-openings, namely one or several combustion chamber through-openings for the cylinder or cylinders of the engine, as well as coolant through-openings and oil through-openings. The gasket plate also has screw holes through which there extend cylinder head screws, with which the cylinder head gasket is clamped between the engine component sealing surfaces of engine block (also called crankcase) and cylinder head. On the side of the engine block, the sealing surface can be formed apart from the actual engine block also by one or several cylinder liners, possibly also by parts of a chain case, and in some multi-cylinder engines a separate cylinder head and a separate cylinder head gasket are provided for each cylinder, and these cylinder head gaskets are then clamped between the engine block (possibly including cylinder liners) and the cylinder heads.
Most of the known cylinder head gaskets of the kind mentioned at the outset have a multi-layer gasket plate consisting, for example, of three sheet metal layers arranged one above the other, the two outer layers of which consist of sheet spring steel and around the through-openings to be sealed are provided with beads which are spring-elastically deformable in their height as sealing elements, for which the center layer is provided with so-called stoppers, i.e., deformation limiters, for preventing the beads from being flattened to too great an extent during clamping of the gasket between the engine component sealing surfaces and during operation of the engine—in view of the dynamic load on the beads during operation of the engine, excessive bead deformation would lead to permanent breakages as a result of crack formation. Such a cylinder head gasket is disclosed, for example, in U.S. Pat. No. 6,135,459. However, such a cylinder head gasket requires quite a considerable width of the so-called sealing gap delimited by the engine component sealing surfaces (when the engine is cold and out of operation)—this spacing of the engine component sealing surfaces from one another is usually referred to as sealing gap dimension or assembly dimension (of the cylinder head gasket). For cost reasons there are endeavors to reduce as far as possible the number of sheet metal layers required for a cylinder head gasket. With a given engine, for which, for example, a three-layered cylinder head gasket has hitherto been used, this results in thicker metal sheets having to be used for gaskets with a smaller number of sheet metal layers, because an otherwise necessary decreasing of the sealing gap dimension would necessitate structural changes to the engine itself, which is not accepted by the manufacturer of the engine. However, a bead in a thicker sheet metal layer must have a greater width (in section perpendicular to the longitudinal direction of the bead) in order to have the same elastic deformation characteristics as a bead formed in a thinner metal sheet, and as the through-openings to be sealed by sealing elements in cylinder head gaskets designed for modern engines often lie very close to one another, in many cases wider beads cannot be realized owing to lack of space.
For the sake of completeness, it will be pointed out that the above-described elasticity of sealing beads with respect to their height is necessary because under the effect of the high combustion gas pressures occurring upon ignition of a cylinder, when the engine is in operation, the cylinder head, which is not an absolutely rigid component, arches somewhat over the cylinder which has just been ignited and, consequently, the spacing of the engine component sealing surfaces from one another around this cylinder becomes greater, i. e., the sealing gap width increases, so that the bead must have the characteristic that when it is relieved of load its height will increase in a spring-elastic and hence reversible manner in order that the bead will not lose its sealing function upon widening of the sealing gap.
The object of the present invention was to develop an alternative sealing element for a cylinder head gasket of the kind mentioned at the outset, which can replace a sealing bead that is elastic with respect to its height, and the width of which is at least substantially independent of the thickness of the metal sheets used for manufacturing the cylinder head gaskets.